Circuit arrangement for demodulating an intermediate-frequency video signal

Abstract

A circuit arrangement for demodulating an intermediate-frequency video signal, comprising a video demodulator (1) and a phase-locked loop (5) formed as a Costas loop, in which an output signal of a controllable oscillator (12) arranged in the Costas loop and the intermediate frequency video signal are coupled to the video demodulator (1), should always supply a demodulated video signal of a predetermined polarity, independent of overmodulation occurring in the intermediate-frequency video signal. To this end, this circuit arrangement is characterized in that a polarity inverter (2) is provided, which is preceded by the video demodulator 1 and by means of which the polarity of the demodulated video signal is invertable in dependence upon a control signal supplied by a polarity detector (3), and in that the polarity detector (3) determines the polarity of the output signal of the video demodulator (1) or of the polarity inverter (2) and, in dependence upon the determined polarity, controls the polarity inverter (2) by means of the control signal in such a way that the demodulated video signal at the output of the polarity inverter (2) has a predetermined polarity.

Dependencies are inferred from the claim text.